Although rapid eye movements (REMs) are a prominent feature of paradoxical sleep (PS), their origin and functional significance remain poorly understood in humans. In animals, including nonhuman primates, REMs during PS are closely related to the occurrence of the so-called PGO waves, i.e., prominent phasic activities recorded throughout the brain but predominantly and most easily in the pons (P), the lateral geniculate bodies (G), and the occipital cortex (O). Therefore, and because the evolution of species is parsimonious, a plausible hypothesis would be that during PS in humans, REMs are generated by mechanisms similar to PGO waves. Using positron emission tomography and iterative cerebral blood flow measurements by H(2)(15)O infusions, we predicted that the brain regions where the PGO waves are the most easily recorded in animals would be differentially more active in PS than in wakefulness, in relation with the density of the REM production [i.e., we looked for the condition (PS versus wakefulness) by performance (REM density) interaction]. Accordingly, we found a significant interaction effect in the right geniculate body and in the primary occipital cortex. The result supports the hypothesis of the existence of processes similar to PGO waves in humans, responsible for REM generation. The interest in the presence of PGO waves in humans is outstanding because the cellular processes involved in, or triggered by, PGO waves might favor brain plasticity during PS. [less ▲]

in Proceedings of the first Internation Conference on Finite Element Methods (2003)

Turbulent wind is a natural and therefore random phenomenon. The analysis of flexible structures subjected to turbulent wind requires, in a finite element approach, the resolution of a system of ... [more ▼]

Turbulent wind is a natural and therefore random phenomenon. The analysis of flexible structures subjected to turbulent wind requires, in a finite element approach, the resolution of a system of stochastic differential equations. It is supposed that the characteristics of the structure are perfectly known; thus the stochastic aspect of the problem comes from the random loading only. As the turbulent wind is most commonly characterized by its frequency content, the resolution of this equation is generally performed in the frequency domain. All governing equations must therefore be linear. If this can be reasonably supposed for the structure, this hypothesis is not mathematically justified for the wind loading. When the non linear behaviour of any part of the structure has to be accounted for, the resolution in the frequency domain is not valid anymore. It is then necessary to compute, with a step-by-step dynamic analysis, the response of the structure to a series of generated wind histories. In a finite element approach, this is for example achieved thanks to Newmark’s or Wilson’s methods. Averaging across the ensemble of the computed time-varying responses allows then to recover statistical results that a stochastic analysis would provide. This analysis method is known as a stochastic Monte Carlo simulation. After having emphasised the need to represent correctly the coherence between wind pressures at different points of the structure, this paper will present a method for generating a set of correlated wind histories that must be used in a finite element analysis. Finally an example of application of the presented method will prove its efficiency. [less ▲]

A small portion of the oxygen consumed by aerobic cells is converted to superoxide anion at the level of the mitochondrial respiratory chain. If produced in excess, this harmful radical is considered to ... [more ▼]

A small portion of the oxygen consumed by aerobic cells is converted to superoxide anion at the level of the mitochondrial respiratory chain. If produced in excess, this harmful radical is considered to impair cellular structures and functions. Damage at the level of mitochondria have been reported after ischemia and reperfusion of organs. However, the complexity of the in vivo system prevents from understanding and describing precise mechanisms and locations of mitochondrial impairment. An in vitro model of isolated-mitochondria anoxia-reoxygenation is used to investigate superoxide anion generation together with specific damage at the level of mitochondrial oxidative phosphorylation. Superoxide anion is detected by electron paramagnetic resonance spin trapping with POBN-ethanol. Mitochondrial respiratory parameters are calculated from oxygen consumption traces recorded with a Clark electrode. Respiring mitochondria produce superoxide anion in unstressed conditions, however, the production is raised during postanoxic reoxygenation. Several respiratory parameters are impaired after reoxygenation, as shown by decreases of phosphorylating and uncoupled respiration rates and of ADP/O ratio and by increase of resting respiration. Partial protection of mitochondrial function by POBN suggests that functional damage is related and secondary to superoxide anion production by the mitochondria in vitro. [less ▲]

We propose a method for generating all symmetric Dicke states, either in the long-lived internal levels of N massive particles or in the polarization degrees of freedom of photonic qubits, using linear ... [more ▼]

We propose a method for generating all symmetric Dicke states, either in the long-lived internal levels of N massive particles or in the polarization degrees of freedom of photonic qubits, using linear optical tools only. By means of a suitable multiphoton detection technique, erasing Welcher-Weg information, our proposed scheme allows the generation and measurement of an important class of entangled multiqubit states. [less ▲]

In this study, we have developed a simple and efficient technique for the isolation of viable lymphocytes from the epithelium and stroma of small pre-neoplastic squamous intraepithelial lesions (SIL) of ... [more ▼]

In this study, we have developed a simple and efficient technique for the isolation of viable lymphocytes from the epithelium and stroma of small pre-neoplastic squamous intraepithelial lesions (SIL) of the uterine cervix. Following the separation of the epithelium from the stroma using dispase II, both biopsy fragments were used to generate T lymphocytes. The stroma-derived lymphocytes were obtained by collecting and culturing the cells migrating out of the biopsy in the presence of IL2 (50 U/ml). An average of 0.7 x 10(6) and 1.4 x 10(6) lymphocytes could be obtained after 20 and 30 days of culture, respectively. For the expansion of lymphocytes derived from the pre-neoplastic epithelium (SIL) it was necessary to use a combination of irradiated peripheral blood mononuclear cells (PBMC) as a feeder layer with PHA (0.1%), in addition to IL2 (50 U/ml). Interestingly, these lymphocytes could be obtained using either allogeneic or syngeneic PBMCs. With this protocol, we were able to generate up to 100 x 10(6) lymphocytes from the epithelium, the majority of which were T lymphocytes. [less ▲]

Filaments are narrow, shallow structures of cool water originating from the coast. They are typical features of the four main eastern boundary upwelling systems (EBUS). In spite of their significant ... [more ▼]

Filaments are narrow, shallow structures of cool water originating from the coast. They are typical features of the four main eastern boundary upwelling systems (EBUS). In spite of their significant biological and chemical roles, through the offshore exportation of nutrient-rich waters, the physical processes that generate them are still not completely understood. This paper is a process-oriented study of filament generation mechanisms. Our goal is twofold: firstly, to obtain a numerical solution able to well represent the characteristics of the filament off Cape Ghir (30°38'N, northwestern Africa) in the Canary EBUS and secondly, to explain its formation by a simple mechanism based on the balance of potential vorticity. The first goal is achieved by the use of the ROMS model (Regional Ocean Modeling System) in embedded domains around Cape Ghir, with a horizontal resolution going up to 1.5 km for the finest domain. The latter gets its initial and boundary conditions from a parent solution and is forced by climatological, high-resolution atmospheric fields. The modeled filaments display spatial, temporal and physical characteristics in agreement with the available in situ and satellite observations. This model solution is used as a reference to compare the results with a set of process-oriented experiments. These experiments allow us to reach the second objective. Their respective solution serves to highlight the contribution of various processes in the filament generation. Since the study is focused on general processes present under climatological forcing conditions, inter-annual forcing is not necessary. The underlying idea for the filament generation is the balance of potential vorticity in the Canary EBUS: the upwelling jet is characterized by negative relative vorticity and flows southward along a narrow band of uniform potential vorticity. In the vicinity of the cape, an injection of relative vorticity induced by the wind breaks the existing vorticity balance. The upwelling jet is prevented from continuing its way southward and has to turn offshore to follow lines of equal potential vorticity. The model results highlight the essential role of wind, associated with the particular topography (coastline and bottom) around the cape. The mechanism presented here is general and thus can be applied to other EBUS. [less ▲]

We propose a scheme enabling the universal coupling of angular momentum of N remote noninteracting qubits using linear optical tools only. Our system consists of N single-photon emitters in a ... [more ▼]

We propose a scheme enabling the universal coupling of angular momentum of N remote noninteracting qubits using linear optical tools only. Our system consists of N single-photon emitters in a configuration that are entangled among their long-lived ground-state qubits through suitably designed measurements of the emitted photons. In this manner, we present an experimentally feasible algorithm that is able to generate any of the 2N symmetric and nonsymmetric total angular momentum eigenstates spanning the Hilbert space of the N-qubit compound. [less ▲]

The Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) spacecraft obtained the first global images of the proton aurora. One of the discoveries from these images was a region of proton ... [more ▼]

The Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) spacecraft obtained the first global images of the proton aurora. One of the discoveries from these images was a region of proton precipitation equatorward of the nominal auroral oval. This precipitation can be observed for similar to10 min immediately following a large solar wind pressure pulse. Various mechanisms have been proposed for producing this precipitation. This study focuses on one of the proposed mechanisms, the scattering and precipitation of protons due to interaction with electromagnetic ion cyclotron (EMIC) waves. Using data from the IMAGE spacecraft FUV and EUV imagers, in situ ring current data from the Los Alamos geosynchronous spacecraft, and in situ solar wind data from the ACE spacecraft, two features of the precipitation, the local time occurrence and limited latitudinal extent, are explained. The local time occurrence of the precipitation is correlated with the orientation of the pressure pulse front in the solar wind. The limited latitudinal extent of the emissions appears to be related to the interaction between the hot ring current protons and the cold plasmaspheric ions that gives rise to EMIC wave growth. [less ▲]